The present invention relates to a semiconductor device and, more particularly, to a semiconductor device which includes a semiconductor chip bonded to an insulating substrate such as a film carrier.
A smiconductor device is proposed in U.S. Pat. No. 3,763,404, "SEMICONDUCTOR DEVICES AND MANUFACTURE THEREOF" patented on Oct. 2, 1973, wherein a semiconductor chip is bonded to lead electrodes formed on a flexible carrier made of, for example, a polyimide film. In the film carrier system, electrodes formed on the semiconductor chip are arranged so as to confront finger lead electrodes formed on the flexible carrier, and the electrodes formed on the semiconductor chip are simultaneously connected to the corresponding finger lead electrodes formed on the flexible carrier through the use of a bonding method.
Therefore, the above-mentioned film carrier system is suited for mass production. Moreover, the film carrier system has great advantages. For example, the film carrier system facilitates the fabrication of thin and small semiconductor devices.
However, the film carrier system of the prior art can not show a sufficient yield. And the semiconductor device formed by the film carrier system of the prior art can not tolerate the mechanical shock. The present inventors have discovered that the above defects are caused by the following facts. Generally, in the film carrier system, wiring patterns essentially made of copper are formed on the film carrier. In order to enhance the tight connection between the film carrier and the wiring patterns, it is necessary that roughness of three to fifteen micron (3-15.mu.m) amplitude be formed on the surface of the copper film confronting the film carrier. One method for forming the roughness on the copper film surface is to mechanically rub the copper film surface. However, when the copper film is formed through the use of plating techniques, roughness of the three to fifteen microns (3-5.mu.m) amplitude is unavoidably formed on the plated surface. Therefore, in the film carrier system, the copper film formed through the use of plating techniques is used to form the wiring patterns.
Accordingly, the finger lead electrode surfaces also have a roughness of the three to fifteen microns (3-5.mu.m) amplitude. This roughness on the finger lead electrodes causes a capillary phenomenon during the bonding treatment Therefore, there is a possibility that an eutectic alloy created during the bonding treatment will flow along the rough surfaces by capillary action to form undersirable short circuits between the finger lead electrodes and the semiconductor chip. The thus formed short circuits will damage the semiconductor chip.
Accordingly, an object of the present invention is to provide an improved thin semiconductor device.
Another object of the present invention is to provide a semiconductor device carried on a film carrier.
Still another object of the present invention is to provide a semiconductor device carried on a film carrier, which shows accurate and stable operation.
Yet another object of the present invention is to provide a semiconductor device carried on a film carrier, which shows a good yield.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, the surface of the finger lead electrodes is smoothed, as compared with that of the wiring patterns, through the use of a mechanical polishing method, a press method, an electrolytic polishing method, or a slight etching method. By smoothing the finger lead electrode surface, the undersirable capillary phenomenon is prevented and, therefore, the semiconductor device can show accurate operation.